Free Chrome extension · ★★★★★ on the Web Store

What key is
this song in?
Answered in 30s.

Key Detector finds the key, mode & BPM of any audio playing in your browser. Tab detection without a mic, nothing uploaded, 100% on your device.

Add to Chrome — it's free Detect the key of a song online →
Tab detection without a mic 100% local No sign-up
Key Detector
Detect, analyze & transpose
Expand ✓ PRO 17

Key detected

D#
MAJOR
0% CONF
★★★★★Chrome Web Store rating
1,000+installs in under 2 months
24keys detected, major & minor
100%local, no audio uploaded

See it in one minute

Find the key, then make the song yours

Detect the key, tempo and chords, see them over the YouTube video, and change the key and speed for free.

How it works

From a song to its key in 3 steps

No account, no upload, no learning curve. Under a minute from install to answer.

  1. 01

    Add it to Chrome

    One click from the Chrome Web Store, then pin it to your toolbar so it's always one click away.

  2. 02

    Play any song

    Open YouTube, Spotify Web, SoundCloud — anything with audio. Hit play and let it run.

  3. 03

    Tap Detect

    Open the popup and hit Detect. In ~30 seconds you get the key, confidence, BPM and the scale lit up on the piano.

The full kit

Five ways to read a song

One popup, every tool a musician needs to figure out what's playing.

Detect · the main event FREE

One tap. A confident verdict.

Key Detector 2.0 analyzes tonal energy over time and compares candidate major/minor keys. Results are estimates: compare alternatives and another passage when the music is ambiguous. Tonal affinity is not a probability of being correct.

  • All 24 major & minor keys, with a color-coded confidence ring
  • Shows 3 alternative keys when it's a close call
  • BPM detected alongside the key — music keeps playing, no muting
D#
MAJOR
0% CONF
Live · real-time FREE

Watch the key as it plays.

Continuous detection that updates every few seconds, with a visual chromagram of all 12 notes. Perfect for songs that modulate.

  • Live key, confidence and BPM
  • Chromagram bar graph of note energy
  • Great for a quick read before committing to a verdict
Studio · transpose YouTube ★ FREE

Slow it down. Change the key.

Transpose YouTube in real time by ±12 semitones, with independent speed control from 0.25× to 2× — powered by a SoundTouch AudioWorklet.

  • Pitch shift without changing speed (and vice-versa)
  • Auto-detects the active YouTube video
  • Built for practice, karaoke and playing along
TRANSPOSE -3 st
-120+12
SPEED 0.75×
0.25×1×2×

Pitch and speed move independently — drag to feel it.

Piano · interactive FREE

See the scale. Hear the notes.

A C4–C5 keyboard that lights up with your detected key. Pick a root and scale, then click any key — it actually plays.

  • Auto-syncs the scale to your verdict
  • Root in bold purple, scale notes in lavender
  • Major, minor & chromatic — fully playable
ROOT
SCALE

Now showing D# Major — click any key to hear it

Tap BPM + Files FREE

Tap the tempo. Drop a file.

Tap along to get the BPM by hand, or analyze audio straight from your computer — fully offline, the file never leaves your device.

  • Tap BPM with outlier rejection (Space to tap)
  • Upload MP3, WAV, FLAC, M4A, OGG, AAC, OPUS
  • Same verdict engine: key, BPM, alternatives, piano
— BPM
Drag & drop an audio file — analyzed 100% offline

Key Detector Pro

Unlock the full studio

Monthly, yearly, or pay once and keep it forever. Here's what comes with Pro.

Chords on every song

Chords over YouTube as it plays and a printable chart with diagrams. Free covers 3 songs a month; Pro has no limit.

Unlimited file analysis

Free gives you 1 upload a week. Pro removes the limit entirely — analyze as many tracks as you want.

Advanced Studio

Sound tools, natural voice, separated tracks, up to 4× and ±24 semitones — the full practice rig.

FEATURE
Free
Pro
Key detection (Detect)
✓
✓
BPM detection
✓
✓
Live real-time mode
✓
✓
Interactive piano
✓
✓
Tap BPM
✓
✓
History
5 results
Unlimited
File analysis
1 / week
Unlimited
Detection 45s / 60s
—
✓
Transpose, speed and A–B loop on YouTube
✓
✓
Chords on the video + printable chart (beta)
3 songs/month
Unlimited
Advanced Studio — sound, natural voice, 4×, ±24, tracks
—
✓
Song library, setlists and sharing
—
✓
Color themes
—
✓
Camelot wheel (best for DJs)
—
✓
Dark mode
✓
✓
Side panel — better view, more control
✓
✓
Cross-device (email login)
—
✓
★ Get Key Detector Pro

Try Pro free for 7 days — no card, start it in one click from inside the extension. Then choose monthly, yearly or a one-time lifetime purchase via Stripe.

New in 2.0

What's new in Key Detector 2.0

Free key and speed changes on YouTube, chords over the video, the side panel, dark mode and a new Pro.

Privacy first

Your audio stays yours

Audio processing stays on your device. Optional usage telemetry and license management are described in the privacy policy.

100% local processing

All analysis runs in your browser. Audio never leaves your device.

Tab detection without a mic

Detect and Live read tab audio without a microphone. In version 2.0, the Free tuner requests microphone access only when you start it and processes audio locally.

No analysis servers

Audio never leaves your device: no uploads, no recordings. Anonymous usage counts help us improve, and you can switch them off in Settings. Buying Pro or starting the trial sends only your email, to ExtensionPay, to manage the licence.

Only when you ask

Detection runs solely when you actively start it. Nothing in the background.

Made for musicians

Who it's for

Guitarists
Play along without tuning by ear
Singers
Find the key, transpose to your range
Producers & DJs
Confirm key & BPM for harmonic mixing
Students
Visualize scales, train your ear
Transcribers
Identify keys in seconds, not minutes
Composers
Analyze reference tracks fast

Works wherever audio plays

YouTube Spotify Web SoundCloud Bandcamp Apple Music …and any site with audio in Chrome

Questions

Everything you might be wondering

How does Key Detector find the key of a song?

Key Detector 2.0 analyzes tonal energy over time and compares candidate major/minor keys. Results are estimates: compare alternatives and another passage when the music is ambiguous. Tonal affinity is not a probability of being correct.

Does it work on YouTube, Spotify and SoundCloud?

Yes. It reads the audio from your browser tab, so it works on YouTube, Spotify Web, SoundCloud, Bandcamp, Apple Music and virtually any site that plays audio in Chrome.

Do I need a microphone?

Detect and Live read tab audio without a microphone. In version 2.0, the Free tuner requests microphone access only when you start it and processes audio locally.

Is my audio private?

Completely. All analysis runs locally in your browser. No audio is uploaded, recorded or stored on any server, and detection only runs when you start it.

Is Key Detector free?

Key detection, BPM, live mode, the interactive piano and Tap BPM are free. Pro is a one-time purchase that adds the Studio YouTube transposer, the Camelot wheel, dark mode, unlimited history and more.

Can I transpose or slow down a YouTube video?

Yes, for free: Studio transposes YouTube in real time by up to 12 semitones (24 with Pro) and changes the speed independently, powered by a SoundTouch AudioWorklet.

Find your first key in 30 seconds.

Add Key Detector to Chrome, open a song, and tap Detect. It's free, it's local, and it just works.

Add to Chrome — it's free See what Pro unlocks